package es.ucm.fdi.pe.practica2.genetico2.mutacion;

import java.math.BigInteger;

class Permutaciones {
	private int[] a;
	private BigInteger numLeft;
	private BigInteger total;
	
	public Permutaciones(int n) {
		if (n < 1) 
			throw new IllegalArgumentException("Min 1");
		a = new int[n];
		total = getFactorial(n);
		reset();
	}
	
	public void reset() {
		for (int i = 0; i < a.length; i++) 
			a[i] = i;
		numLeft = new BigInteger(total.toString());
	}
	
	public BigInteger getNumLeft() {
		return numLeft;
	}
	
	public BigInteger getTotal() {
		return total;
	}
	
	public boolean hasMore() {
		return numLeft.compareTo(BigInteger.ZERO) == 1;
	}
	
	private static BigInteger getFactorial(int n) {
		BigInteger fact = BigInteger.ONE;
		for (int i = n; i > 1; i--) 
			fact = fact.multiply(new BigInteger(Integer.toString(i)));
		return fact;
	}
	
	public int[] getNext() {
		if (numLeft.equals(total)) {
			numLeft = numLeft.subtract(BigInteger.ONE);
			return a;
		}
		int temp;
		// Find largest index j with a[j] < a[j+1]
		int j = a.length - 2;
		while (a[j] > a[j + 1])
			j--;
		// Find index k such that a[k] is smallest integer
		// greater than a[j] to the right of a[j]
		int k = a.length - 1;
		while (a[j] > a[k]) 
		k--;
		// Interchange a[j] and a[k]
		temp = a[k];
		a[k] = a[j];
		a[j] = temp;
		// Put tail end of permutation after jth position in increasing order
		int r = a.length - 1;
		int s = j + 1;
		while (r > s) {
			temp = a[s];
			a[s] = a[r];
			a[r] = temp;
			r--;
			s++;
		}
		numLeft = numLeft.subtract(BigInteger.ONE);
		return a;
	}
	
	public static void main(String[] args) {
		int[] indices;
		//String[] elements = { "a", "b", "c", "d" };
		int [] elements = {1,2,3};
		Permutaciones x = new Permutaciones(elements.length);
		//StringBuffer permutation;
		while (x.hasMore()) {
			//permutation = new StringBuffer();
			indices = x.getNext();
			for (int i = 0; i < indices.length; i++) {System.out.println("Vez "+(i+1));
				System.out.println(elements[indices[i]]);
				//permutation.append(elements[indices[i]]);
			}
			//System.out.println(permutation.toString());
		}
	}
} 
